In the field of high-speed printing devices which are especially suitable for use in connection with electronic data processing systems, the wire matrix type of printer has come into increasing use. In this type of printer, letters, numbers and symbols are formed from a series of dots produced by the impact of the ends of a plurality of wire elements on record media.
Since the wires employed in the matrix printer have a short operating stroke, it is important that a uniform distance be maintained between the print head and the upper surface of the medium being printed upon. It is therefore important, in those cases in which a plurality of different thicknesses of record media may be printed upon by a matrix printer, to provide a compensating device which acts to maintain the same relative distance between the print head and the upper surface of the record media regardless of changes in the thickness of the record media.
Various compensation devices for maintaining a predetermined distance between the print head and the record media regardless of the thickness of the record media are known in the prior art. In some of these, print head guide rollers are run along a flexible tape secured at its ends. In another arrangement, an axially reciprocable probe is used to determine the position of the surface of the record media to be printed upon, and controls a motor which positions the print head accordingly.